Robert Babington: Nebulizer fuel burner (US Patent # 4573904,
etc)

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**Robert S. BABINGTON**

**Nebulizer**

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 **[N. Metzger: "Clog-Proof Superspray Oil Burner"
~ Popular Science (January 1976)](#popsci)**   
**[R. Babington: US Patent # 4,573,904 ~ Liquid
Delivery Apparatus & Method for Liquid Fuel Burners](#4573)**
  
**[R. Babington: US Patent # 4,155,700 ~ Liquid
Fuel Burners](#4155)**   
**[R. Babington: US Patent # 3,425,058 ~ Fuel
Burner](#3425)**   
**[R. Babington: US Patent # 3,4228,795 ~
Apparatus for Producing Finely Divided Liquid Spray](#4228)**   
**[R. Babington: US Patent # 3,864,326 ~ Spraying
Devices, in Particular Nebulizing Devices](#3864)**   
**[R. Babington: US Patent # 3,790,080 ~ Method of
Spraying](#3790)**   
**[R. Babington: US Patent # 3,425,059 ~ Power
Humidification Apparatus](#3425)**   
**[R. Babington: US Patent #3,421,692 ~ Method of
Atomizing Liquids...](#3421)**   
  


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**Popular Science (January 1976) ~** ****"Clog-Proof Superspray Oil
Burner"** **by** **Norman Metzger****

*A new type of nozzle promises fuel savings of up to 15%*

"Were in the midst of an energy crisis", inventor Robert
Babington reminded me at his home in this Washington suburb.
"And if you ask what the advantage of this device is, its a 15%
saving in fuel oil."

The device Babington was describing is an oil-burner head with
a revolutionary new spray nozzle (PS, May 1973). In addition to
its remarkable fuel-saving potential, Babington claims oil
furnaces using his invention wont soot up, will never clog, and
can even run on crankcase oil and diesel-fuel mixture.

Experts Ive talked to back up the claims for the oil burner,
which could one day shave your fuel costs two ways:

(1) Fuel can be burned more evenly and completely, because it
is converted into a superfine, uniform spray.

(2) Heavier, less-costly oil can be used; the burners
operating principle makes it independent of fuel viscosity.

The secret behind the new oil burner is in the unique
properties of the burner head. Most nebulizing sprayers (misting
sprays used for everything from medical tents to insecticides)
use compressed air to spray liquids through a nozzle.

Babington, a former NASA engineer, reversed that principle. He
forces only air through one or more tiny slots in a bulb. The
air breaks up any liquid flowing over the slot into minute
particles. Since no liquid goes through the slot, theres no
clogging problem. And, unlike conventional sprays, the viscosity
or thickness of the liquid isnt critical. Babington gave me a
dramatic illustration: one by one, he poured motor oil,
turpentine, and paint thinner over a flaming oil-burner head.
The flame kept going in spite of the liquid used.

Burning Crankcase Oil

Whats important is surface tension. Almost any liquid fuel
will burn, since most have similar surface tensions. Babington
explained what this implies: "With this burner, a gas stateion
could take compressed air, mix its crankcase oil with diesel
fuel or kerosene, burn it, and see no real difference in
performance compared to what theyre getting today from straight
diesel fuel [See "Adventures in Alternate Energy", PS June
1975]."

Theres solid support for the oil burner from people who have
taken a hard look at it. "We field-tested about 50 of them",
says Rix Beals, technical consultant to the National Fuel Oil
Institute (NOFI), the trade association for home-heating oil
dealers. "Even though we had teething problems in these field
tests", Beal said, "most of the men who tested these burners are
still bugging us, asking when theyre going to get to market,
because they want them". NOFI has backed the Babington burner
with cash -- about $250,000 in direct and indirect funds -- in
the effort, as yet unsuccessful, to market the new burner.

NOFI, a subsidiary of the National Oil Jobbers council, has
also looked at costs for the Babington burner. "There was a
range of values", Beals told me, "and at every point we felt it
could be produced at no more -- and apparently in many cases a
good deal less -- than conventional burners."

"I dont see whats wrong with it", adds Gerald Leighton, who
at the time was Chief of Energy and Utilities Applications for
the US Dept. of Housing and Urban Development (HUD). "Its low
cost. Its efficient. The potential for life-cycle costs looks
excellent. And I havent seen a comparable device."

Despite the enthusiasm, however, theres still no manufacturer
for the burner. Babington made his first working model of the
burner in 1967, using part of an aquarium pump and a sewing
machine motor. He then licensed the burner to an aerospace
company trying to diversify into consumer products.

Eventually another company was set up to market the burner, but
it was run by people who "didnt understand the basic principles
of the device", according to Babington. He saw their product for
the first time at a 1972 Washington trade show. To his horror,
it had a host of problems: sooting, poor ignition, and too long
a flame; ultimately, the burner was rejected by Underwriters
Laboratories. "If you give the wheel to the wrong team, they
wont be able to roll", is the way Babington sums up that
episode.

Babington has since recovered the license to his burner and has
made basic changes that, according to Beals, "solve some of the
problems we ran into in the field tests".

Two Heads Are Better...

Babington stopped the sooting by moving the igniters out of the
spray zone. He added a second atomizing head or bulb; two sprays
and thus two flames are contined in one burner head. The two
sprays meet to produce what Babington calls a "really beautiful
fire".

NOFIs Beals agrees: "The double atomizing head is definitely
an improvement. By using two flames firing at each other", he
explains, "you create a fixation or stabilizing point for the
flames out in space. The electrodes now have a point at which to
create ignition. So, the burner will start better than any
previous model; it will start almost instantly without any pop
or puff.

"The fixation point", Beals adds, "makes the flame more stable,
less bothered by drafts, and more reliable. That burner should
ignite literally thousands of times in sequence without
misfiring."

The savings, Beals explained, come largely from the very fine
oil mist produced in the Babington burner. A homeowner could
save some $60 a year, based on the national average annual
consumption of 1200 gallons for each home at 25 cents/gallon.

"We knew", says Beals, recalling NOFIs long search for a
better burner head, "that the touchstone to improvement was
atomization, the quality of the drops produced. Not only how
fine they are, but also how uniformly fine. If you have a fog of
fine droplets, it ignites easier and you should be able to use
less power in your ignition system.

"There were other atomization techniques, but for the most part
they were not reliable, And they added cost, weight and power
draw. They had a lot of negatives, and besides did very little
to eliminate the clogging problem."

When Beals and his NOFI team tested the Babington burner, they
found that at practical flow rates (one-half to one
gallon/hour), it achieved a finer droplet size than any other
atomization technique they had found.

The finer droplet size means easier ignition. It also means
less air is needed for complete ignition and a more manageable
flame. All this adds up to a better burning fuel. As evidence
for this, Babington cites two things: a 14.5% carbon dioxide
level instead of the average 9% for conventional burners, and a
lack of smoke.

The new burner, Babington and Beals say, can replace existing
heads in almost any oil furnace. Most of these are "gun
burners", named after the shape of a high-pressure oil pump and
pressure nozzle. Those nozzles do a heck of a good job, Beals
says, but they do clog and do not atomize fuel the way a
Babington burner will.

Whats next? "Its at the point", Beals told me, "where --
possibly with some alternate control and ignition systems -- you
can make some manufacturing decisions, and then sit down and
design a final manufactured form".

Meanwhile, Babington is working on other things, including a
vaporizing burner, one that atomizes the fuel completely, not
just into small droplets. The fuel is then burned as a gas would
be.

He showed me a model of this vaporizing burner; its secret is
that the liquid fuel is kept vaporized until it reaches the
ignition point. Once again, Babington did it by installing two
atomizing heads in his burner, but his time he made one smaller
than the other. The spray from the smaller head is ignited
instantly as it comes out of the bulb. It intersects the second
larger -- and unlit -- spray. The latter, however, does not
ignite because it doesnt have enough air. Heat from the smaller
flame keeps the second spray vaporized, and it ignites when it
finally "sees" enough air, or when a second set of igniters
turns it on.

Vaporizing burners already developed sometimes use heated
plates to vaporize fuel poured over them. This creates problems,
including soot and smoke. Babington claims his "free-stream
vaporizing burner" doesnt have these problems. He acknowledges
the burner needs more work before its ready to try commercial
waters.

****Medical Nebulizers****

The engineer has already shown he can take his invention along
the treacherous seas from a good idea to a commercial product.
The Babington principle is the heart of several commercial
nebulizers marketed by American Hospital Supply Corporations
McGaw Laboratories. The devices have captured about 10% of a $5-
to $6-million-a-year market.

Babington is also working on additional medical and health
applications of his nebulizing spray. Hes created a "medicant"
nebulizer. With each breath, a patient inhales mist and
medication through a disposable mouthpiece. And a working mode
of his "home-therapy console" is in his workshop, too. Switches
convert it to either a nebulizer or humidifier, and change the
amount, intensity, and temperature of the mist.

For now, Babingtons hopes -- and those of quite a few others
-- are riding with the new oil burner he created some 8 years
ago. "Its been a long, slow struggle with this thing", recalls
Beals. "And its been mainly a matter of finding the right
company. But weve never given up hope we can get to market
because its one of the things we need. And we need it more now
than we did 5 years ago."

The 170 gallons average that would be saved annually by each
home oil burner outfitted with a superspray nozzle could make a
significant contribution to our national fuel reserves. The
question now is whether we can afford to neglect it for even
another season.

****How Superspray Works****

Liquid washing over the outside surface of a small glass or
plastic bulb forms a thin surface film. Air forced through one
or more slots in the bulb breaks the liquid into a fine spray
(right) that can shoot out 6 feet or more. Key advantages of
sprayer principle: Uniformity of particle size and the
elimination of clogging. A second atomizing bulb has been added
to improve efficiency.

**---

  

**US Patent #,573,904**

**Liquid Delivery Apparatus & Method
for Liquid Fuel Burners and Liquid Atomizers****

Abstract

An improved apparatus and method for delivering liquid are
disclosed for use in fuel burners or atomizers of the type which
comprise a hollow atomizer bulb having a convex exterior surface
which tapers toward a small aperture through which high pressure
gas if forced to atomize liquid as it flows in a thin film over
the bulb. To provide thinner films when lower atomization rates
are desired and thicker films when higher atomization rates are
desired, a feed tube is positioned above the atomizer bulb with
its discharge opening oriented so that the vertical distance
from its front edge to the surface of the bulb is from 1.5 to
2.0 times the vertical distance of its rear edge to the surface
of the bulb. In another embodiment the discharge opening of the
feed tube is elongated and has a major axis oriented
transversely to the axis of the spray leaving the aperture.

References Cited   
U.S. Patent Documents:   
3425058 ~ Jan., 1969 ~ Babington ~ 431/117   
4155700 ~ May, 1979 ~ Babington ~ 431/117

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to three other applications
filed concurrently and entitled Flow Control Module and Method
for Liquid Fuel Burners and Liquid Atomizers (two applications)
Ser. No. 476,292 and Ser. No. 476,455 and Improved Atomization
Apparatus and Method for Liquid Fuel Burners and Liquid
Atomizers Ser. No. 476,454, now U.S. Pat. # 4,507,074; #
4,516,928; and # 4,507,076 respectively.

TECHNICAL FIELD

The present invention concerns liquid fuel burners and liquid
atomizers and methods of operating such burners and atomizers.
The apparatus and method of the invention are particularly
related to liquid feed systems for burners and atomizers of the
type which incorporate an atomizer bulb having a smooth, convex
exterior surface tapering toward an aperture. A flow of air or
other gas is directed through the aperture to atomize fuel or
other liquid as it flows in a thin film over the exterior
surface of the atomizer bulb.

BACKGROUND ART

In January 1969, U.S. Pat. # 3,421,692; # 3,421,699 and #
3,425,058 issued to Robert S. Babington, the present applicant,
and his co-inventors. These patents disclose a type of liquid
atomization apparatus which is particularly useful in liquid
fuel burners. The principle involved in the apparatus, now
frequently referred to as the "Babington principle," is that of
preparing a liquid for atomization by causing it to spread out
in a free-flowing thin film over the exterior surface of a
plenum having an exterior wall which defines the atomizer bulb
and contains at least one aperture. When gas is introduced into
the plenum, it escapes through the aperture and thereby creates
a very uniform spray of small liquid particles. By varying the
number of apertures, the configuration of the apertures, the
shape and spray characteristics of the surface, the velocity and
amount of liquid supplied to the surface, and by controlling the
gas pressure within the plenum, the quantity and quality of the
resultant spray can be adjusted as desired to suit a particular
burner application. Various arrangements of such atomization
apparatus have been disclosed in other U.S. patents issued to
the present applicant, namely U.S. Pat. # 3,751,210; #
3,864,326; # 4,155,700; and # 4,298,338. The disclosures of the
patents mentioned in this paragraph are specifically
incorporated by reference into this application.

So that liquid fuel burners and liquid atomizers constructed in
accordance with the Babington principle will have the widest
possible range of applications, it has been found desirable to
provide the maximum possible variation in the volumetric flow
rate of the atomized fuel or other liquid between the lowest and
the highest flow rates required. For example, flow rates as low
as 0.3785 liter (0.1 gallon) per hour may be required for some
applications and as high as 3.785 liters (1.0 gallon) per hour
may be required for others.

Once the particular geometry for a given atomization apparatus
has been selected, however, changes in the flow rate of the
atomized liquid must be made primarily by adjusting the flow
rate of liquid onto the atomizer bulb. For the lowest flow rates
desired, the liquid film thickness at the aperture preferably
would be the thinnest achievable while still maintaining a
continuous film over the exterior surface of the atomizer bulb.
On the other hand, to provide higher flow rates of the atomized
liquid, it is necessary to increase the thickness of the film at
the aperture without increasing it so much that undesirably
large liquid particles are formed. In the prior art apparatuses,
a single liquid feed tube has been positioned above each
atomizer bulb a distance of approximately 3.175 to 9.53 mm
(0.125 to 0.375 inch) so that a variable flow rate of atomized
liquid from about 0.757 to 2.27 liters (0.2 to 0.6 gallons) per
hour has been achievable. Various applications have remained,
however, in which flow rates above and below this range have
been desired but have not been reliably achievable.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide an improved
apparatus and method for delivering liquid fuel to an atomizer
bulb which operates in accordance with the Babington principle
so that both higher and lower flow rates can be achieved than
have been found possible with prior art atomizer bulbs.

Another object of the invention is to provide such an apparatus
and method in which the high intermediate and low flow rates
produce essentially stable films at the aperture of the atomizer
bulb.

A further object of the invention is to provide such an
apparatus and method in which entrained gases or bubbles in the
liquid are shed immediately from the feed tube delivering the
liquid to the atomizer bulb and also from the surface of the
atomizer bulb, to eliminate undesirable fluctuations in the
liquid film flowing over the atomizers and, hence, fluctuations
in the firing rate, which the presence of such bubbles would
otherwise tend to cause.

Yet another object of the invention is to provide such an
apparatus and method for feeding liquid fuel which can be used
with atomizer bulbs made in accordance with the Babington
principle but which have a variety of convex surfaces which
taper toward the atomizing aperture.

These objects of the invention are given only by way of
example; therefore, other desirable objectives and advantages
inherently achieved by the disclosed apparatus may occur or
become apparent to those skilled in the art. Nonetheless, the
scope of the invention is to be limited only by the appended
claims.

The apparatus and method according to the invention are
particularly adapted for delivering liquid fuel or other liquid
to an atomizing means of the type which includes a plenum having
an exterior wall with a small aperture therethrough, the
exterior surface of this wall being smooth and convex and
tapering toward the aperture. A feed tube is provided through
which liquid is to be flowed over the exterior surface and
across the aperture, the tube having a downwardly directed,
essentially straight portion with a center line. The straight
portion terminates above the plenum with a discharge opening
which is positioned with its front edge closer to the aperture
than its rear edge and with the extended center line of the tube
reaching a convex portion of the exterior surface of the plenum.

In one embodiment, the vertical distance from the front edge of
the discharge opening to the convex portion preferably is about
1.5 to 2.0 times the vertical distance from the rear edge to the
exterior surface. As a result of this configuration, when liquid
flows through the feed tube at flow rates sufficient just to
cover the exterior surface of the plenum with a thin film
suitable for low atomization rates, a bulbous-shaped stream is
established between the discharge opening and the surface of the
atomizer bulb. The bulbous-shaped stream preferentially directs
itself more away from the aperture than would a stream flowing
parallel to the discharge leg of the feed tube. On the other
hand, when liquid flows through the tube at relatively high flow
rates sufficient to smoothly cover the exterior surface of the
plenum with a thicker film suitable for higher atomization
rates, the stream between the discharge opening and exterior
surface preferentially directs itself toward the aperture. At
liquid flow rates in between these minimum and maximum
conditions, the path of liquid leaving the feed tube is parallel
to the axis of the discharge leg of the feed tube, as one might
expect. Thus, a thinner film is formed over the aperture at
lower flow rates through the feed tube due to the bulbous effect
and a thicker film is formed over the aperture at higher flow
rates through the feed tube because of a forward deflection of
the liquid, so that respectively lower and higher flow rates of
atomized liquid can be achieved.

In this embodiment of the invention, the plane of the discharge
opening of the feed tube is horizontal; however, it is also
within the scope of the invention to position the rear edge of
the discharge opening below the front edge. In such a case, the
vertical distance from the front edge of the tube preferably is
at least equal to the inside diameter of the feed tube. In order
to ensure smooth flow from the discharge opening of the feed
tube, its downwardly directed, essentially straight portion
preferably has length about 10 to 15 times the inside diameter
of the tube.

In another, preferred embodiment of the invention, the
discharge end of the otherwise cylindrical feed tube is
flattened into a somewhat "duckbill" configuration having a flow
area shaped as an elongated oval with major and minor axes. The
plane of this oval discharge opening preferably is essentially
parallel to a plane tangent to the upper surface of the atomizer
bulb with the major axis of the oval discharge opening
preferably essentially perpendicular to the spray axis of the
atomizer bulb. In this preferred embodiment, the stable minimum
film thickness at the aperture is less than can be reliably
achieved with the previously described embodiment, for the same
minimum flow rate through the feed tube. Also, a greater, stable
maximum film thickness can be achieved at the aperture with a
smaller maximum flow rate through the feed tube, than can be
reliably achieved with the previously described embodiment. In
the latter case, less fuel must be recirculated at the maximum
atomization rate, so that reduced pump capacity is needed. In
addition, the reduced liquid flow over the atomizer bulb
provides better film stability and causes the drain-off liquid
stream to be more or less laminar, thereby facilitating its
removal and return to the sump. This preferred embodiment is
also very effective in shedding bubbles that might otherwise
hang up in the space between the atomizer bulb and the discharge
end of the feed tube.

In the preferred embodiment, the sensitivity of the film
thickness at the aperture of the atomizer bulb to changes in the
flow rate in the feed tube decreases dramatically as the major
axis of the oval discharge opening is rotated from a position
perpendicular to the spray axis to a position parallel to the
spray axis. In the latter, limiting case, the film thickness at
the orifice remains essentially stable regardless of changes in
the flow rate in the feed tube. However, when the major axis of
the oval discharge opening is parallel to the spray axis, the
feed system continues to resist formation of bubbles between the
feed tube and the atomizer bulb.

BRIEF DESCRIPTION OF THE DRAWINGS

![](fig1-6.gif)

FIG. 1 shows a fragmentary elevation view of an atomizer bulb
which operates in accordance with the Babington principle, a
feed tube for liquid fuel positioned above the atomizer bulb in
accordance with one embodiment of the present invention and the
associated air and fuel sources and ignition device necessary to
comprise a complete fuel burner.

FIG. 2 shows a fragmentary elevation view of a liquid fuel
atomizer according to one embodiment of the present invention
and particularly illustrates the direction of flow of fuel away
from the atomizing aperture at low fuel flow rates.

FIG. 3 shows a fragmentary elevation view of a liquid fuel
atomizer according to one embodiment of the present invention
and particularly illustrates the flow of the fuel toward the
atomizing aperture at high fuel flow rates.

FIG. 4 shows an elevation view of a tubular blank used to make
a feed tube for use in the preferred embodiment of the
invention.

FIG. 5 shows an elevation view of a feed tube according to the
preferred embodiment of the invention, in the preferred position
above the automizer bulb.

FIG. 6 shows a section view taken on line 6--6 of FIG. 5.

FIG. 7 shows an elevation view of an alternative configuration
of a feed tube according to the preferred embodiment of the
invention, as positioned above the atomizer bulb.

BEST MODE FOR CARRYING OUT THE INVENTION

The following is a detailed description of several embodiments
of the present invention, reference being made to the drawing in
which like reference numerals identify like elements of
structure in each of the several Figures.

FIG. 1 shows a system for atomizing liquid fuel or other
liquid, which operates in accordance with the Babington
principle. An atomizer bulb 10 comprises an enveloping, convex
exterior wall 12 which defines an internal plenum (not
illustrated) and includes a frontal aperture 14, typically a
narrow horizontal slit passing completely through the exterior
wall. A source 16 of high pressure air or other gas is connected
to the plenum defined by exterior wall 12 by means of a conduit
18 so that in operation a flow of air is caused to pass through
aperture 14. Positioned above atomizer bulb 10 is a liquid feed
tube 20 which preferably has a circular cross-section but may
also have other cross-sections without departing from the scope
of the present invention. Liquid drawn from a sump 22 through a
conduit 23 by a pump 24 is caused to flow through a further
conduit 25 into feed tube 20 from which it flows over atomizer
bulb 10 and forms a film of liquid which completely covers the
surface of bulb 10. As air flows through aperture 14, the film
of liquid continuously forming at the aperture is continuously
broken into tiny droplets of liquid which move away in the form
of a fine, conical spray 26 of atomized liquid. Liquid not
atomized to form spray 26 flows from the lower side of bulb 10
as a stream 28 which is directed back to sump 22, as
illustrated. To complete the schematic illustration of a fuel
burner, FIG. 1 also shows an igniter 30 which extends to spray
26 at a downstream location in order to ignite the fuel in the
manner described more completely in the previously-mentioned
patents.

In prior art liquid fuel burners and liquid atomizers which
operate in accordance with the Babington principle, the firing
rate of the burner, or the atomizing rate, is varied by changing
the volumetric flow rate of liquid in spray 26. In a typical
prior art application, a flow of approximately 7.6 to 45.4
liters (2 to 12 gallons) per hour through feed tube 20 results
in a spray flow rate or firing rate of approximately 0.76 to
2.27 liters (0.2 to 0.6 gallons) per hour. The change in flow
rate through feed tube 20 causes a corresponding change in the
thickness of the film reaching aperture 14 so that a change in
firing or atomizing rate is achieved.

In accordance with the embodiment of the present invention
shown in FIGS. 1 to 3, the position of feed tube 20 is selected
so that at the lower flow rates through feed tube 20, the stream
of liquid leaving the feed tube is preferentially directed away
from aperture 14 so that a thinner film is produced at aperture
14 than has heretofore been achievable. Conversely, at the
higher flow rates through feed tube 20, the stream of liquid
leaving the feed tube is preferentially directed toward aperture
14 so that a thicker film is achieved.

As shown in FIG. 1, feed tube 20 has an essentially straight
portion 32 which extends downwardly toward atomizer bulb 10 and
includes a centerline, as illustrated. The length L of portion
32 preferably is ten to fifteen times the internal diameter D of
feed tube 20 that any irregularities in flow through the feed
tube 20 will have dissipated, for the most part, by the time the
liquid issues from discharge opening 34. In accordance with this
embodiment of the invention, the front edge 36 of discharge
opening 34 is positioned further away from the surface of bulb
10 than is the rear edge 38 of discharge opening 34; and the
center line of portion 32 is positioned so that it passes
through a convex area of exterior wall 12 as illustrated. Wall
12 preferably has an exterior surface which is smooth, convex
and tapered toward aperture 14. As used in this application,
"convex" means that geometric normals will diverge when
constructed at neighboring points on the "convex" portion of
bulb 10. Thus, at the tip of atomizer bulb 10, the exterior wall
12 may be spherical having a radius R, ellipsoidal, hyperbolic,
parabolic, and so forth. The portion of bulb 10 to the rear of
the center line of feed tube 20 may be a right circular
cylinder, a frustrum of a cone whose sides diverge at an angle
.beta. or the other half of a sphere, ellipsoid, paraboloid or
the like.

In accordance with the invention, the vertical distance V.sub.f
from front edge 36 to exterior wall 12 and the vertical distance
V.sub.r from rear edge 34 to the surface of wall 12 are chosen
so that V.sub.f is approximately 1.5 to 2.0 times larger than
V.sub.r. In this embodiment, front and rear edges 36 and 38 are
in a common horizontal plane; however, it is also within the
scope of the invention to position point 38 below point 36, or
vice versa, as indicated by angle .alpha. in FIG. 1. Whether
.alpha. is positive (i.e., edge 38 below edge 36) or negative as
would be the case if edge 36 was below edge 38, depends upon the
flow rate through tube 32, and the amount and size of air or gas
bubbles contained in the liquid stream. If the burner is to be
operated at generally lower firing rates a positive .alpha. is
preferred, whereas at higher firing rates a negative .alpha. is
preferred. In general it is easier to shed large air bubbles
when .alpha. is positive, but the corresponding film is not as
stable at high flow rates. Because of these tradeoffs, and the
desirability of a burner to handle a variety of fuels over a
wide firing rate range, an .alpha. of 0.degree. is often
selected as a happy medium and for ease of manufacturing.

When feed tube 20 is configured and positioned in the manner
just described, the flow of liquid through discharge opening 34
displays unexpected and important characteristics. FIG. 2
illustrates the position assumed by the stream of liquid leaving
discharge opening 34 when the flow through feed tube 20 is at
the lowest possible flow which still achieves a complete film on
the exterior surface of bulb 10. As shown in FIG. 2, the stream
takes on a rearwardly directed bulbous shape which
preferentially directs fuel away from aperture 14 because the
bulbous stream touches the atomizing surface closer to edge 38
than to edge 36. This occurs because the axis of leg 32
intersects the convex surface of atomizer bulb 10. As a result,
the film of liquid fuel formed at aperture 14 is quite thin and
the firing or atomizing rate is proportionately smaller. As the
flow of liquid through feed tube 20 is increased, the stream
leaving discharge opening 34 gradually assumes a more vertical
position as illustrated in FIG. 1 and the amount of liquid
leaving in spray 26 increases accordingly. Finally, as
illustrated in FIG. 3, when the flow through feed tube 20 is
increased to the maximum consistent with maintaining a smooth
film of liquid on the exterior surface of bulb 10, the stream of
liquid leaving discharge aperture 14 preferentially shifts
itself toward the front of atomizer bulb 10. This causes a
relatively thicker film to form at aperture 14 which results in
a correspondingly higher flow of liquid in spray 26.

The following dimensions represent some typical values for a
liquid fuel atomizer, according to the embodiment of FIGS. 1 to
3, which will produce a variable atomization rate from about 1.1
to about 3 liters (0.29 to about 0.79 gallons) per hour based on
fuel feed rates of about 7.5 to 45 liters (1.98 to 11.89
gallons) per hour through feed tube 20. A typical atomizer bulb
10 has an essentially spherical convex portion having an outside
diameter of about 10.2 to 1.5 mm (0.4 to 0.6 inches) The
cross-sectional area of discharge aperture 14 typically is about
10.97.times.10.sup.-4 to 12.26.times.10.sup.-4 cm.sup.2
(1.7.times.10.sup.-4 to 1.9.times.10.sup.-4 square inches) and
the pressure applied to the interior of atomizer bulb 10
typically is in the range of 1.02 to 1.6 bar (15 to 23.5 psi).
The spacing between the lower end of feed tube 20 at rear edge
38 and the surface of atomizer bulb 10 preferably is from about
1.78 to 2.54 mm (0.070 to 0.100 inch). The spacing between the
forward edge 36 of the feed tube and a vertical line through
aperture 14 is normally between 1.02 to 1.65 mm (0.040 to 0.065
inch) while the internal diameter of tube 32 is between about
2.16 to 2.54 mm (0.085 to 0.100 inch). Liquid fuel atomizers
thus configured and operated have been found to exhibit the
desired flow switching characteristics when operated with liquid
fuels having a viscosity range of 2.0 to 10.0 centistokes.

FIGS. 4 to 7 show the preferred embodiment of a liquid fuel
delivery apparatus according to the invention. Here, feed tube
20 is formed from a blank 20', shown in FIG. 4, for example made
from about 3.18 mm (0.125 inch) outside diameter, about 2.36 mm
(0.093 inch) inside diameter stainless steel tubing. Blank 20'
has a horizontal upper portion 40 and a downwardly extending,
forwardly angled portion 42. The angle .gamma. between portions
40 and 42 preferably is about 100.degree., but may be in the
range of 90.degree. to 110.degree. without departing from the
scope of the invention. So that the plane of the discharge
opening of the feed tube ultimately will be essentially parallel
to a plane tangent to the upper surface of an atomizer bulb of
the type previously described, the discharge end 44 of blank 20'
preferably slopes upwardly and rearwardly at an angle .delta. of
about 20.degree., but may slope at an angle in the range
10.degree. to 30.degree. without departing from the scope of the
invention.

In the preferred embodiment of the invention, discharge end 44
of blank 20' is flattened transversely to the plane of the
center lines of portions 40 and 42, as shown in FIGS. 5 and 6,
to provide a short flow passage 46 and discharge opening 48
having a flow area shaped as an elongated oval with a major axis
50 and a minor axis 52. For a blank 20' of the size and material
previously described, the tube is squeezed until the minor axis
52 is approximately 1.4 mm (0.055 inch) and the major axis is
3.30 mm (0.130 inch). The axial length of flow passage 46, the
"duckbill" portion of the feed tube, preferably is in the range
of 6 to 9 mm (0.250 to 0.350 inch) to ensure that any flow
irregularities induced by the change in cross-section will be
adequately damped by the time the fuel discharges from opening
48.

A feed tube configured as shown in FIGS. 4-6 preferably is
positioned directly above atomizer bulb 10 so that the plane of
the discharge opening 48 is 0.51 to 0.76 mm (0.020 to 0.030
inch) above the surface of the atomizer bulb; the leading edge
of opening 48 is 5.1 to 6.4 mm (0.200 to 0.250 inch) behind
aperture 14; and major axis 50 is essentially perpendicular to
the spray axis 54 of the atomizer bulb. In this configuration,
the thickness of the film at aperture 14 varies smoothly from a
minimum at a flow rate through feed tube 20 of about 7.6 liters
(2.0 gallons) per hour corresponding to an automization rate of
about 0.56 liters (0.15 gallons) per hour, to a maximum at a
flow rate through feed tube 20 of about 30 liters (8.0 gallons)
per hour corresponding to an atomization rate of about 3.8
liters (1.0 gallons) per hour. Bubbles in the fuel do not tend
to adhere between discharge opening 48 and the upper surface of
atomizer bulb 10, primarily because of the close spacing between
end 48 and the surface of atomizer 10.

As major axis 50 is rotated relative to spray axis 54, while
maintaining essential parallelism between the plane of discharge
opening 48 and a plane tangent to the upper surface of the
atomizer bulb, the thickness of the film at aperture 14 and the
corresponding atomization rate vary less and less with changes
in the flow rate through feed tube 20. When duckbill portion 46
is positioned so that major axis 50 is essentially parallel to
spray axis 54 as shown in FIG. 7, virtually no change in
atomization rate is experienced due to changes in the flow rate
through feed tube 20. Thus, the configuration of FIG. 7 may be
preferable where substantial fluctuations in flow are
anticipated in conduit 25 and where the burner is to be operated
at an essentially constant fuel rate. However, the atomization
rate remains essentially stable in this limiting case and
bubbles in the fuel do not tend to adhere between discharge
opening 48 and the upper surface of atomizer bulb 10, for the
same reasons as previously mentioned.

Industrial Applicability

While the present invention has been disclosed as particularly
suited for use in liquid fuel burners, those skilled in the art
will recognize that its teachings also may be followed for other
applications of the Babington principle where it is desired to
obtain a maximum variation in the flow rate of the vaporized
liquid.

**---

  
**US Patent 4,155,700** **Liquid Fuel Burners****

Abstract --- An improved fuel burner particularly adapted for
domestic use and capable of burning fuels such as fuel oil and
the like with extremely high efficiency and low pollutant output
is comprised of a pair of identical spray heads, each including
a spherical plenum onto which the fuel is flowed for
atomization, the spray heads being disposed at the end of a
flame tube which in turn is located within a blast tube, said
spray heads further being disposed symmetrically with respect to
the axis of both the flame tube and the blast tube and angularly
disposed relative to each other whereby the spray output from
the spray heads creates a turbulence within the flame tube such
that the propagation of the flame front within the tube can be
readily controlled and whereby the fuel may be readily ignited
by a spark type of ignitor which is disposed centrally between
the spray heads. The plenum is provided with one or more
apertures through which atomizing gas is passed to generate the
spray, and air access ports are so located in the flame tube
such that substantially complete combustion of the fuel is
effected.

References Cited   
U.S. Patent Documents:

1577114 ~ Mar., 1926 ~ De Walt ~ 239/543   
1910615 ~ May., 1933 ~ Laney ~ 239/543   
3067582 ~ Dec., 1962 ~ Schirmer ~ 431/117   
3425058 ~ Jan., 1969 ~ Babington ~ 431/117   
3539102 ~ Nov., 1970 ~ Lang ~ 239/434   
3595482 ~ Jul., 1971 ~ Loveday ~ 239/434   
3923251 ~ Dec., 1975 ~ Flournoy ~ 431/351   
4035137 ~ Jul., 1977 ~ Avand ~ 431/351   
4036582 ~ Jul., 1977 ~ Fehler et al. ~ 431/352

Primary Examiner: Yuen; Henry C. ~ Attorney, Agent or Firm:
Pollock, Vande Sande & Priddy

Description

PRIOR ART AND BACKGROUND

As is well recognized in the industry, there has long been a
need to develop and to provide a fuel burning system which is
capable of burning a liquid fuel in a very efficient manner and
without the side effects of inadequate combustion which lead to
the omission of pollutants into the atmosphere.

In the case of residential oil burners, the burner must operate
with low smoke emissions to prevent sooting of the heat
exchanger and objectionably high smoke levels in residential
neighborhoods. The result is that large amounts of excess air
must be introduced in the residential combustion process to
assure that the burner operates at acceptable smoke levels.

It is well known that conventional oil burners burn very
differently when they are placed in different type furnaces.
This is because of the poor fuel atomization of current high
pressure oil burners, which when installed in a furnace, cause
some of the oil particles that discharge from the nozzle to be
very large. These large particles take time to vaporize and burn
and may therefore, fall to the bottom of the combustion chamber
without burning. When the combustion chamber is cold, these
large particles form a puddle in the bottom of the combustion
chamber. When the combustion chamber is heated, these large
droplets or, in some cases, puddles of fuel, eventually vaporize
and burn.

There will be more or less puddling or spattering of large
particles on the walls of the combustion chamber, depending upon
the particular combustion chamber design and the temperature
within the firebox. As a result, the combustion chamber or
firebox, in a normal home furnace, acts as an afterburner to
burn large particles of fuel because the atomization system in a
conventional gun burner cannot by itself adequately atomize the
fuel.

An oil burner may be 2-3 times larger than is necessary to
provide adequate space heating when it is intended that the same
burner shall be used to provide hot water in addition to space
heating. When outside temperatures are low and hot water demands
are high, the burner must be able to satisfy both of these
requirements when the demands are at a peak. However, when the
demand for heat is low, as in the spring and fall months, and
hot water demands are at a minimum, as would be the case at
night, the burner still operates at the same firing rate as it
does when heating and hot water demands are high. The only
difference is that when the requirements are low, the burner may
only stay on for quite short period. This is an inefficient mode
of operation since, under these conditions the burner cycles on
and off many times so that fuel economy is very low. During this
short on cycle with such a burner, the burner cannot achieve
smokeless operation, and reasonable efficiency, before the
thermostat cuts it off. During "off" cycle, much of the residual
heat in the furnace is dissipated to the atmosphere and
contributes to increased fuel costs.

An innovative approach to fuel burners is illustrated in U.S.
Pat. # 3,425,058, issued Jan. 28, 1969, to Robert S. Babington.
The burner therein disclosed represents an adaptation of the
liquid atomization principles disclosed in U.S. Pat. # 3,421,699
and  # 3,421,692 issued Jan. 14, 1969, to the same named
inventor and his co-inventors in developing the apparatus and
method shown in these patents.

In brief, the principle involved in the aforementioned patents
is that of causing a liquid to be atomized to flow over a
surface in a highly stressed state, either due to surface
tension or due to the particular configuration given to the
surface upon which the liquid is discharged.

The surface upon which the liquid is flowed is generally the
outside of a plenum chamber having one or more very small
apertures over which the liquid flows in a continuous film. Air
is introduced into the plenum and passes through the aperture
and thereby causes a phenomena in the film whereby very fine
micro-sized particles of the liquid are caused to separate from
the film in substantial numbers.

By such variations as increasing the number of apertures, the
configuration given the apertures, the characteristics of the
surface, the regulation of the liquid flow, and/or the
regulation of the air pressure, it has been found that not only
can great numbers of micro-sized particles be generated but they
can be generated in such density that it is impossible to
penetrate the resulting spray with light.

It is this basic principle, described above, that was utilized
in the development of the very burner disclosed in said U.S.
Pat. # 3,425,058.

In the above-mentioned patent, the developmental burner
comprised of simply a cylindrical chamber having a cover
thereover, the cover being provided with an aperture adapted to
discharge spray generally vertically from the chamber. Disposed
within the chamber is a spherical plenum having a lower
cone-shaped appendage, the chamber being in communication with a
source of air. Liquid is introduced into the chamber so as to
flow over the surface of the sphere and drain downwardly along
the appendage to a funnel disposed beneath the appendage. The
fluid not expended in the combustion process is then discharged
back to a sump for recirculation into the liquid system. The
plenum is provided with a small aperture centrally located
beneath the opening in the cover and the air exiting therefrom
creates a fine mist which is discharged upwardly and out of the
container for mingling with the atmosphere and combustion occurs
at that point.

Means comprising a series of regulatable apertures are also
provided in the container below the sphere such that aspirated
air can be drawn into the chamber and mingled with the spray as
it discharges from the top opening.

From this very simple version of a fuel burner was derived more
sophisticated equipment, such as that shown and discussed in an
article in the January 1976 issue of Popular Science; entitled
"Clog-Proof Super Spray Oil Burner". As noted in the article,
one development that evolved was the use of two atomizing heads
arranged to discharge the atomized liquids toward one another to
create a very high concentration of atomized liquid at a fixed
point at which is disposed an ignitor to initiate the combustion
process.

A similar arrangement of opposed spray heads is also suggested
in U.S. Pat. #3,864,326, dated Feb. 2, 1975.

All of the above noted developmental work based on the
utilization of the "Babington" principle proved conclusively
that the system was perfectly capable of use in a fuel burning
system and that, if properly designed, such a system has the
potential of evolving into a commercial, practical, highly
efficient fuel burner which can be used for domestic heating
furnaces. This invention, then, deals with a novel fuel burner,
particularly adapted for use in practically every type of
domestic heating furnace and in particular, as a retrofit burner
for existing heating systems. Grade or fuel oil can be burned
with 95% efficiency and at a zero smoke factor within thirty
seconds or less from the time of ignition.

SUMMARY OF THE INVENTION

The present invention, the inefficiencies associated with many
on-off burner cycles are eliminated. By simply controlling the
liquid film thicknesses over the atomizing surfaces as will be
described, the firing rate of the burner can be modulated over a
typical range of 5-1. This means that the same burner, without
changing atomizers, can be modulated either manually or
automatically to match the heating and/or hot water loads. For
example, during modestly cool spring and summer evenings, the
burner can be set to operate at a firing rate of 0.3 gal/hr. and
during cold winter days when hot water is required, the same
burner can be adjusted to consume fuel at a rate of 1.5 gal/hr.
These adjustments can be made manually by simply adjusting the
fuel flow rate over the atomizing spheres by means of a simple
valve in the liquid feed line, and by making a corresponding
adjustment to the combustion air delivered to the flame tube. In
the most sophisticated version of the novel burner disclosed
herein, these adjustments can be made automatically with
suitable control techniques readily available on the market.

Another object of the present invention is to produce an oil
burner whose firing rate can be simply modulated either manually
or automatically to suit the heating demand.

Another object of the invention is to produce a burner that
performs with high efficiency regardless of the combustion
chamber that it is placed into and therefore is ideally suited
as a retrofit or replacement burner for existing furnaces.

Still another object of this invention is to produce a oil
burner that will permit substantial reductions in energy costs
when retrofitted into existing furnaces.

Still another object of this invention is to produce an oil
burner with exceptionally stable flame front.

Another object of the invention is to produce a burner that is
capable of operating at low firing rates, as for example less
than 0.5 gal/hr. without clogging problems.

The burner of this invention comprises a cylindrical blast tube
housing concentrically therein a flame tube to define an annular
air passage therebetween said passage being closed at one end by
an annular plate; the opposite end of said passage being closed
by a second annular plate having apertures therein, said flame
tube being open at said first mentioned end and being provided
with a perforated closure having a large central aperture at the
second mentioned end; atomizing heads being provided to
discharge through said perforated closure, said flame tube
having apertures therein located at relative angular positions
to stage air into the flame tube to control the shape of the
emitted flame.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is now made to the appended drawings and the detailed
description which follows, showing one preferred mode of
practicing the invention;

FIGS. 1A and 1B are a schematic view of a typical heating
furnace or firebox and showing the utility of the present
invention as compared to the usual prior art apparatus;

![](fig1-2.gif)

FIG. 2 is a front end view of a fuel burner assembly as
utilized in the firebox referred to in FIG. 1;

FIG. 3 is a vertical section view taken along the line 3--3 of
FIG. 2 and showing details of one of the spray heads, and

![](fig3-4.gif)

FIG. 4 is a sectional plan view taken approximately along the
line 4--4 of FIG. 2 and showing details of the flame tube
assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Deferring descriptions of FIGS. 1A and 1B momentarily,
consideration will first be given to FIGS. 2 and 4 which show
the improved fuel burning assembly. As shown in FIG. 4, a
conventional blast tube 1, which is essentially an elongated
open ended pipe disposed in the firebox of the furnace, supports
concentrically therein a flame tube 3 supported on a plurality
of annular rings 5 and 7 such that the flame tube 3 is located
concentrically with respect to the blast tube to define an
annular air passage therebetween. The flame tube 3 is open at
both ends, one end 9 facing 1 toward the firebox of the furnace
or the like, the other end facing toward the exterior of the
firebox and upon which the spray heads are mounted and, as is
also the oil and air supply motors and compressors carried in a
suitable housing.

The open end 9 of the flame tube 3 is provided with a pair of
cutouts 13, 13', the function of which will become apparent
subsequently. Similarly the flame tube is provided with a
further pair of apertures 12, 12' located approximately midway
of its length. These apertures are disposed at 90.degree.
relative to the cutouts 13, 13'.

The cylindrical flame tube 3 is provided at its opposite end 11
with a pair of spray heads 30 and 30' which are defined by
cuplike atomizing chambers 15, 15', respectively.

The atomizing heads are supported upon a foraminous fire wall
14, which is shown as being generally cone shaped, said wall
being provided with a relatively large central aperture 16
passing through the wall 14 at its center.

Projecting through the central opening 16 in wall 14 and
disposed midway between the atomizing heads 30, 30' is a
conventional spark igniter 18 which includes a pair of discharge
electrodes 19 and 21. The igniter may be supported by a suitable
bracket and, of course, is energized from a source of high
voltage electricity.

As shown in FIGS. 3 and 4, the chambers 15, and 15'
respectively, may be provided with discharge cones 17 and 17'
which discharge atomized fuel inwardly into the flame tube 3.

FIG. 3 shows that each atomizing chamber 11 is provided with a
pair of conduits 23' and 25' which are, in essence, elbows
having one end projecting into the chamber along a generally
vertical plane passing immediately through the walls thereof.
The uppermost conduit 23' defines a fuel supply conduit while
the lower conduit 25' defines a drain-off conduit, the functions
of both of which will be apparent subsequently.

Disposed directly below each fuel supply conduit 23' and
supported on the rear wall 31' of the chamber 15' is a spherical
plenum chamber 26' which is supplied with air under pressure
through conduit 27', which also extends through the rear wall
31' of the cup-shaped vaporizing chamber 15'. The plenum
chambers 26, 26' is provided with at least one being small
aperture 29', only one shown in FIG. 3, which is located so as
to discharge air directly toward the discharge horn 17'.

As clearly shown in FIG. 3, the rear wall 31' of the vaporizing
chamber 15' is provided with an aperture 33' whose function will
be described in detail hereinafter.

Though not shown, it is to be understood that each inlet
conduit 23' are connected to a source of liquid fuel by means of
a pump, whereby the fuel may be pumped through these conduits
and deposited on the spherical surfaces of the plenum chamber
26'. Similarly, the drain or discharge conduit 25' is connected
to the fuel supply system so that liquid which is not atomized
within these chambers can be returned to the fuel system not
shown and recirculated therein.

The description given above with specific reference to spray
head 30' of FIG. 3 applies in identical fashion to spray head 30
shown in FIG. 4.

MODE OF OPERATION AND COMPARATIVE DATA

Directing attention now particularly to FIGS. 3 and 4, the
operation of the improvement in fuel burning heads is as
follows.

Liquid fuel is introduced into the system by the conduits 23,
23'. The liquid fuel flows over the plenum chambers 26, 26' and
a portion thereof is atomized by air under pressure which is
introduced into the plenum through the conduit 27. Liquid which
is not atomized flows to the bottom of the chambers 15, 15' and
is withdrawn therefrom by conduits 25, 25' for recirculation in
the fuel supply system.

As described above, the atomizing heads utilize the basic
"Babington" liquid atomization system disclosed in prior
mentioned U.S. Pat. # 3,421,699 and # 3,421,692.

Due to the discharge of air from the plenum chambers through
apertures 29, there is created a venturi effect as the air fuel
mixture projects outwardly and is discharged through discharge
horns 17 and 17' where such horns are provided. In order to
enhance this effect, air enters the ports 33, 33' and is drawn
along with the atomized fuel into the flame tube 3. Combustion
air is supplied through the aperture 16 in the foraminous fire
wall 14 and provides combustion air so that the turbulent
mixture that results when the two sprays from atomizers impinge
beyond the horns will readily ignite when the igniter 18 is
energized to cause a spark between electrodes 19 and 21.

Additional combustion air passes along the annular passage
between flame tube 3 and blast tube 1 and is staged into the
interior of the flame tube 3 through the staging ports 12 and
the cutouts 13, 13'.

The unique configuration of the flame tube within a blast tube
provides a unique heat exchanger in which combustion air for
staging purposes passes through the annular area between the
flame tube and the blast tube. In traversing this route, the
combustion air picks up heat from the inner hot walls of the
flame tube. This hot air, as it is delivered to the interior of
the flame tube at the two aforementioned staging locations,
helps to promote rapid vaporization of the atomized fuel to
complete the combustion process downstream in the flame tube.
The staging of combustion air in this manner allows the
temperature within the flame tube to be maintained at the
desired level to keep nitrous oxide emissions to a minimum.

Still another advantage of the manner in which the combustion
air is staged is to produce a flame which, when emitted from the
burner, is short and bushy. This is achieved by introducing said
staged air in a non-symmetrical manner which is contrary to the
fuel/air mixing technique used in conventional residential type
oil burners. For example, at the first combustion air staging
location, downstream from the spray impingement site, two air
blast may be introduced perpendicular to the long axis of the
blast tube, at 3 o'clock and 9 o'clock location. By subjecting
the flame within the flame tube to a non-symmetrical air blast
of this type, the flame is caused to squirt out and fill the
flame tube at the 6 o'clock and 12 o'clock position.
Furthermore, the low static pressure within the air blasts at
the 3 and 9 o'clock positions causes the flame to wrap around
the air blasts and thus produce a shorter and more compact flame
which fills the entire flame tube. In the second combustion air
staging location, two air blasts are introduced at the lip of
the blast tube but this time the air blasts are introduced at
the 12 o'clock and 6 o'clock positions. This causes the flame to
spread out in the 3 o'clock and 9 o'clock position as it leaves
the burner blast tube and enters the combustion chamber. A short
bushy flame of this type is ideal for a retrofit or replacement
burner, because it is suited for use in any type of combustion
chamber. This is in contrast to a long thin flame which would
impinge upon the back side of many combustion chambers and cause
erosion of the combustion liner. At the same time, the
combustion air passing between the flame tube and the blast tube
serves to keep the outer blast tube cool, thereby preventing
heat erosion of the blast tube. In the case of the present
invention, the atomization system is so efficient, and the
subsequent fuel/air mixing and vaporization is likewise carried
out in such a highly efficient manner, that the burner does not
require a hot combustion chamber to achieve high combustion
performance. The present burner design has been utilized in a
wide variety of different combustion chambers and has always
been able to achieve smokeless operation, and flue-gas CO2
levels between 14-141/2%, when operating at a firing rate which
is close to that of the furnace rating. Even when the present
burner is set to operate at firing rates well below the furnace
rating (e.g. burner operating at 0.5 gal/hr. in a 1.0 gal/hr.
furnace) CO2 levels with smokeless operation will
normally never fall below 13%.

This is in contrast to the average conventional home oil burner
that operates at CO2 levels of 8% even when the burner firing
rate is matched to the furnace capacity. These characteristics
of total independence of furnace design and furnace temperature
makes the present invention ideal as a replacement or retrofit
burner. This non-dependence on furnace temperature also means
that the present burner will achieve smokeless operation the
instant ignition occurs and before the combustion chamber
becomes hot. The typical conventional high pressure burner takes
several minutes for the smoke level to drop to acceptable levels
after ignition has occurred.

Another fact to be noted is that conventional high pressure
nozzles have difficulty operating at firing rates below
approximately 0.7 gal/hr. without encountering a high incidence
of clogging. In the present burner, there is essentially no
minimum firing rate that can be attained; a prototype burner has
been operated at a firing rate of 0.5 gal/hr. This means that
each individual atomizer is operating at approximately one-half
that firing rate. Further, it is not necessary, in the present
burner, that both atomizers be generating the same amount of
fuel spray for the burner to operate efficiently. For example,
one atomizer may have a firing rate of 0.3 gal/hr. while the
other has a firing rate of 0.2 gal/hr. A burner of this type
will operate just as efficiently as one in which each atomizer
is delivering a spray rate of 0.25 gal/hr. This low firing rate
capability of the present invention is very important in light
of the present energy crisis because homes in the future will be
built with better insulation and the trend is towards low firing
burners that can provide highly efficient operation.

It should be noted that the perforations in the fire wall 14
are so numbered and sized that a very soft flow of air passes
through this wall. This soft air flow tends to keep products of
combustion from filtering or rolling back toward the spray heads
and the igniter, thus inhibiting sooting of these elements.

The included angle between the atomizing heads 30, 30' is shown
in FIG. 4 as being approximately 90.degree.. This angle can be
varied, however, and may be between 45 deg and 150 deg.

Turning now to FIGS. 1 and 1A, it will be noted that in the
prior art the atomizing nozzles are located close to the
interior of the firebox. Consequently, the nozzles are subjected
to high temperatures. Due to this fact, the nozzles are subject
to varnish depositions and clogging are continually subject to
soot and dirt and varnishing caused by decomposition of the fuel
due to its exposure to the heated parts which results in a
varnish deposit being laid down on the atomizing nozzles and
those parts which are disposed within the firebox.

In contrast, utilizing applicant's improved fuel burning head,
the atomizing heads are located well inwardly of the end of the
blast tube and are thus not subjected to the radiant and
convective heat of the firebox. Since the parts then remain
virtually cool, there is little decomposition of the carbons in
the fuel and hence there is little or substantially no
varnishing to interfere with proper atomization of the fuel or
operation of the atomizing parts.

**---

  

**US Patent # 3,425,058**

**Fuel Burner****

Abstract --- The disclosure relates to liquid fuel burners
wherein the fuel to be consumed is supplied to and dispersed
from a film forming surface in spherical shaped droplets of
spray, the excess fuel supplied to the surface being
recirculated.

Disclosure

The invention is concerned with a fuel burner of the atomizing
type and in particular with a liquid fuel burner which is
universally adopted to cause efficient combustion of any liquid
fuel.

An object of the invention, then is to produce a liquid fuel
burner with a high combustion efficiency that will not
deteriorate with the operation of the burner.

Another object of the invention is to produce a liquid fuel
burner capable of burning almost any fuel in liquid form,
without changing the burner configuration or spray head.

Still another object of the invention is to produce a simple
reliable liquid fuel burner

A further object of the invention is to provide a novel
recirculating type of fuel burner.

Still an additional object of the invention is to produce a
liquid fuel burner of extreme simplicity wherein the fuel does
not pass through any nozzle and therefore is not susceptible to
clogging with dirty fuel.

An additional object of the invention is to produce a fuel
burner for liquids in which the rate of combustion can be easily
and quickly regulated.

Another object of the invention is to produce a liquid fuel
burner capable of burning large amounts of fuel and releasing a
large amount of heat energy in small compact combustion
chambers.

Still a further object of the invention is to produce a simply
gravity or pressure fed, low air pressure liquid fuel burner.

These and other objects of the invention not specifically set
forth, but inherent therein will become readily apparent from a
consideration of the subject matter which is directed to a
liquid fuel burner comprising a plenum chamber having a source
of pressurized air connected therewith; a liquid fuel source,
means for admitting fuel from said source onto the outer surface
of said plenum chamber, the point of application of said liquid
being spaced from the aperture a distance sufficient to permit
the fuel to form as a film on said surface before and after
encountering said aperture, a housing surrounding said plenum
chamber, said housing comprising  an apertured chamber and
a closure, said closure being provided with at least one
dispensing opening aligned with said aperture whereby the liquid
may be discharged from said housing and burned externally
thereof and means for collecting excess fuel draining from said
plenum surface for recirculation thereover.

Having thus described the invention in broad aspects, the
operation and details thereof will become apparent from the
following detailed description, wherein reference is made to the
drawings in which,

Figure 1 is a side elevational view in section, showing the
fuel burner, the fuel and air pressure sources being illustrated
schematically,

![](3425a.gif)

Figure 2 is a plan sectional view taken along the line 2-2 of
Figure 1,

![](3425b.gif)

Figure 3 is an elevational view of a modified diffuser in
assembly,

Figures 4a-c are top views showing various diffuser assemblies,

Figure 5 is a top plan view of a modified cover or shroud
assembly, and

Figure 6 is a sectional view taken along the line 6-6 of Figure
5.

Considering, now, Figure 1 in detail, it may be seen that the
burner is comprised of a chamber 1, of generally cylindrical
form and having a closed bottom 3. Chamber 1 is also provided
with a top 5 having a central opening 7 provided, as shown with
an upwardly flared peripheral wall 19. While the chamber is
illustrated as cylindrical and the top as generally dome shaped,
it should be noted that the invention is not so restricted since
any convenient wall and top configuration is possible. A
cylindrical form, however, is most easily fabricated as is the
domed top 5.

Top 5 is provided with a downwardly depending cylindrical skirt
11 adapted to frictionally engage the interior of the chamber
wall to retain same in place.

Disposed within chamber 1 is a funnel-like fuel collector 13.
This collector is positioned concentrically in the chamber and
may be held in place by any suitable support means. In the
embodiment of the invention shown, the collector 13 is supported
on an elbow like drain tube 15 which is simply a hollow tube
having one branch connected to the collector 13 and disposed
vertically and the other branch fixed to the chamber 1 and
extending therethrough to define a fuel return outlet 17.

Also disposed within chamber 1 and preferable concentric
therewith and with respect to collector 13, is a fuel diffuser
assembly 20.

The fuel diffuser assembly is formed by an uppermost and
spherical chamber 21 having at least one aperture 23, provided
in its surface. In the embodiment disclosed this aperture is
disposed at the uppermost point in the spherical surface and as
will be explained later may take a variety of forms. In addition
as will be discussed, more than one aperture may be provided.

The spherical chamber 21 is open at its bottom and this opening
communicated with a generally tube shaped chamber 25 having a
closed bottom in the shape of a downturned cone or point 27.
This cone or point is disposed generally over the center of the
fuel collector 13.

Extending radially outwardly from chamber 25 is a tubular
conduit 29 which is fixed to the wall of chamber 1 and
terminated outwardly thereof, whereby the hollow sphere 21 and
tubular chamber 25 are placed in communication with a source of
gas pressure, outside of chamber 1. The diffuser assembly 20,
then, comprises a closed plenum supported within chamber 1.

Also extending through the wall of chamber 1 radially thereof
is a further tubular conduit 31 having an inward terminal end 33
disposed adjacent but spaced from the spherical surface of
chamber 21. It should be noted that conduit 31 is positioned so
as to lie on a diameter extending through the center of the
sphere.

Surrounding chamber 1 is an annular or hoop-like collar 35.
This collar may be positioned on the outside of the chamber by
any suitable means, friction detents such as 27, so that while
same is prevented from sliding down the cylindrical chamber, it
may be readily rotated with respect thereto. The collar 35 is
further provided with at least one, preferably more --- two
being shown --- apertures 39, 39 in the form of windows which
may be displaced at a variety of angular positions around
cylinder 1.

It will also be seen that the cylindrical wall of chamber 1 is
provided with windows 41, 41 located so as to be disposed
within the vertical dimension of the collar 35 but having an
opening area commensurate with that of the windows 39 in the
collar. Thus as the collar is rotated the window or as shown
windows 39, 39 and 41, 41 can be brought into and out of
registry to any desired degree, the collar 35 serving as a
damper as it is rotated and registry between the windows is
reduced or obviated completely. As shown in Figure 2, the collar
35 is positioned so that about half of the window areas 39, 39
and 41, 41 are registered.

As illustrated schematically in Figure 1, the conduit 31 is
supplied by fuel under pressure from reservoir S, via pump P1.
In some cases the liquid fuel may be passed directly from
reservoir S to conduit 31 provided a suitable gravity flow head
is established between reservoir S and conduit 31.

As is also shown, conduit 29 is supplied with gas from a
pressure source shown simply as pump P2, tough this may be a
charged gas container or any suitable means capable of supplying
gas under pressure at about 3 to 20 psig over sustained periods
of time.

Conduit 17 which defines the fuel return conduit also enters
into pump P1 and is returned to reservoir S through, again
depending on the location of the reservoir S with respect to the
burner, this pump P1 may be dispensed with. In other words,
while a workable system is disclosed the burner is not
inflexible tied in with any particular system of supply and
return so long as the requisite mediums fuel and a gas under
pressure are supplied to conduits 31, 29 respectively and
unburned fuel is removed from collector 13 via conduit 17.

As illustrated in the drawings, the burner may be made of
glass. However, any suitable material may be used to fabricate
these structural parts. For example, the chamber 1 may be
stainless steel while the fuel collector is made of similar
materials; the diffuser being glass or vice versa. Similarly the
diffuser can be made of stainless or other metallic or even
plastic material. Moreover, as will be seen the material may be
governed by the type of fuel being burned so that whatever the
fuel the burner construction is resistant to solvent action or
corrosion by the fuel. Thus, because glass is relatively inert
and almost totally unaffected by any fuel and because the burner
is adaptable to the combustion of practically every known fuel
from gasoline through bunker C oil, it has been illustrated as
formed of glass components.

In Figure 3, however, a modified version is shown wherein the
diffuser assembly is comprised partly of metal, partly of
nonmetallic material to further illustrate the versatility of
the structure.

As shown in Figure 3 there are various means by which the basic
structure may be adapted to accommodate various fuels,
combustion rates, etc. Figure 3 illustrates one such means, it
being understood that same is merely exemplary of one mode
effecting this result. In this figure a diffuser, assembly 20
is shown in partial elevation and the spherical upper portion
thereof, 21 is affixed to the lower member 25 by means of a
threaded connection. As seen in Figure 1, the diffuser sphere is
provided with an opening 23 shown as a round hole having an
outwardly divergent circumferential wall. The wall would of
course be straight, i.e., define a cylinder concentric with the
central axis of the assembly 21, however for reasons of greater
efficiency it is generally preferred that the aperture be
defined by an outwardly opening conical or divergent wall.

By connecting the spherical portion 21 of diffuser assembly
20 to the lower portion 25, by means of a threaded or
push-pull type connection, it is possible to change the sphere
quite easily. Thus, if as will be explained, it is desired to
change the material of the sphere 21 this can be readily
accomplished by substituting one sphere for another. Also where
it is desired to produce a greater burner capacity and/or modify
the flame configuration, sphere 21 may be modified to include
more than one aperture 23 the apertures themselves being varied
from round holes to elongated slots disposed in various
locations in the uppermost portion of the spherical surface.
Examples of various modifications are shown in Figures 4a, b and
c, showing a plurality of diffusers 40, 50 and 60 provided with
apertures 43, 53, and 63 respectively. It will be noted that in
Figure 4a the apertures are in the form of slots disposed at
equally spaced locations around the surface of the sphere. Four
such slots are shown in this embodiment. In Figure 4b the
apertures 53 are in the form of round apertures 53 at
diametrically spaced points on the surface of the sphere 51.
Figure 4c sows the opening 63 as a slot disposed parallel to the
direction of fuel flow. In this connection it should be noted
that fuel flow in these figures is illustrated by the arrows.

From the foregoing descriptive matter, it is believed apparent
that while a simple structural embodiment and several variations
thereof have been shown, the burner is capable of various
modification and changes as will be readily understood as the
mode of operation is described.

In respect of the burner operation, the fundamental concepts
involved in producing a spray characterized by the spheroid
shape of the miniscule drops is described in great detail in
copending applications Ser. No. 605,777 and 605,779, both filed
Dec. 29, 1966. Basically the process involves the introduction
of the fluid to be sprayed on an apertured surface with
sufficient kinetic energy to cause the liquid to film out or be
stressed during its flow over the surface. At the point where
the dynamic film is stressed to a high degree -- as evidenced by
its smooth almost invisible flow pattern -- air at very modest
pressures is emitted from an opening and small almost perfectly
shaped spheroid particles of the liquid are caused to emerge
from the film. Experimentation has shown that these particles of
liquid are on the order of 50 microns in size where, for
example, water is caused to flow in a thin film over a glass
surface and air at a pressure of 8 psig is caused to flow
through a small orifice in said glass surface. In the operation
of the disclosed apparatus it generally requires less energy or
gas pressure to atomize a liquid fuel than it does to atomize
water. This is because virtually all liquid hydrocarbon fuels
have a low surface tension and excellent wetting
characteristics. Good wetting is helpful in the forming of a
highly stressed film and a low surface tension allows the liquid
particles to be easily dispersed from the thin film. For
example, because of these favorable physical properties,
gasoline can be atomized better at a gas pressure of 3 psig than
water can be atomized at a gas pressure of 8 psig.

Surprisingly enough, it has been found that if the liquid is
introduced onto a film forming surface with sufficient kinetic
energy, not only will the liquid flow and spread downwardly as
where it is introduced at a point above the surface, but if, as
shown, the liquid is ejected against a properly curved surface
such as the spherical portion of the diffuser assembly 20, from
fuel inlet pipe or conduit 33, the fluid can be caused and will
flow upwardly to completely envelop the upper portion of the
spherical surface and is highly stressed into a thin dynamic
film which passes over the apertures or aperture 23. If, then,
air at very low pressures above the ambient pressure in the
chamber is cause dto flow through the aperture 23 or apertures
23, 45, 53 and 63, there occurs a separation of miniscule drops
of liquid from the highly stressed dynamic liquid film. As
stated, evidence indicated the drops of droplets are almost
uniformly dispersed as to size and shape, being spheroids on the
order of 50 microns or less.

While the entire phenomenon is not clearly understood, it has
been found that if the spray  thus produced is caused to be
ejected upwardly through a shroud or cover 5, as shown in figure
1 and air is introduced into the chamber 1 through ports 41 as
secondary or combustion air, the diffused liquid will be exited
in great volume through the aperture 7 in shroud 5 and if
ignited the liquid fuel burns with a highly intense combustion
rate about one-half to three-quarters of an inch above the
aperture 7 and will not propagate itself back into chamber 1.
This phenomenon has manifested itself with a variety of liquids
including highly volatile fuels such as gasoline. One
explanation is that the quantity of atomizing air is so small by
comparison to the quantity of fuel atomized, that the fuel/air
mixture within chamber 1 is "fuel rich" that is the fuel/air
ratio is so unbalanced by the presence of excess fuel, that
combustion is impossible. Once the fuel is ejected from the
chamber, however, due to the fineness with which it is
dispersed, the attainment of a favorable combustion ration is
quite rapid with the consequence that burning occurs quite close
to the point of exit of the spray and throughout the entire
spray area.

Because of the above described phenomenon, it is possible to
regulate the spray pattern and volume by means of the cover or
shroud 5 by the simple expedient of providing multiple,
selectively usable covers in which the dimensions of the spray
exit aperture 7 is varied from one cover to another. Thus, by a
matching of a selected opening 7 with the fuel being burned not
only can the combustion rate be readily and easily varied by not
only the cover change but by coupling this feature with a
selection of anyone of the diffuser designs as exemplified in
Figure 4. It has been found that the spray, hence combustion
pattern can be varied from an almost vertical column to a an
shaped pattern.

The quantity of fuel spray and the shape of the spray cloud can
also be controlled by rotating collar 35 to allow more or less
secondary air to enter chamber 1 through windows 41 and 41. Air
is induced to flow into these windows by the ejector or pumping
action of the total spray cloud leaving the fuel burner. The
small amount of atomizing air by itself provides very little
pumping action. However, when combined with the mass flow of the
atomized liquid, a significant amount of secondary air is
induced to flow into chamber 1, when windows 41 and 41 are in
the open position. By restricting the flow through windows 41
and 41 by the rotation of collar 35, the degree of vacuum in
chamber 1 can be controlled. The vacuum control in chamber 1 can
be in turn used to regulate the quantity and shape of the spray
cloud leaving the fuel burner. For example, rotating collar 35
to restrict the secondary flow into chamber 1 through windows 41
and 41 has the effect of increasing the degree of vacuum inside
chamber 1 which in turn reduces the quantity of fuel spray and
suppresses the height of the spray plume. It should be noted
that while significant secondary air flows into chamber 1 during
operation of the burner with side windows 41 and 41 wide open,
this amount of air-flow is not sufficient to generate a
combustible fuel/air mixture inside chamber 1.

In order to further simplify the structure, a modified shroud
or cover 73, such as that shown in Figures 5 and 6 may be used.
Again the mode of carrying out the structural manifestation of
the inventive concept is exemplary only and not limiting. Other
and equivalent means will readily occur to those skilled in the
art. However, turning to Figures 5 and 6 it will be seen that
cover 73 is plane surfaced and provided with a central opening
77 of rather large diameter. Disposed above the opening and
retained on the top surface of the shroud or cover 73 by means
of simple L-shaped lugs 79 are a plurality of segment-shaped
slidable restrictors 81, 83, 95 and 87. Each restrictor may be
provided with an adjustment knob noted generally by the numeral
89. It will be noted that the edges of restrictors 83 and 87
underlie the edges of restrictors 81 and 85, whereby while each
restrictor may be moved inwardly and outwardly with respect to
the center of aperture 77 the restrictors acting as a whole form
a solid shield or mask which rests on top of cover 73. As will
now be obvious movement of the restrictors inwardly has the
effect of reducing the overall diameter of the exit aperture
through the cover 73 and vice versa. In other words, restrictors
81, 83, 85 and 87 define an iris-like shield whereby the
effective area of the aperture may be readily reduced to meet a
desired set of conditions.

Having thus described the invention and various aspects
thereof, it is believed obvious that a variety of modifications
thereof can be made, such being within the spirit and scope of
the inventive concepts involved; these being limited only as
defined in the appended claims.

[Claims not included here]

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**US Patent # 4,228,795** **Apparatus for Producing Finely Divided Liquid Spray****

Abstract --- Apparatus for producing finely divided liquid
particles which includes two chambers having means for conveying
liquid from one chamber to the other and back again to the first
chamber in response to a means for producing a pressure
differential between the chambers. A hollow apertured plenum
chamber having a smooth outer surface is positioned so that the
liquid impinges on its exterior surface as it traverses its flow
path. Gas is supplied under pressure to the interior of the
plenum and ruptures the thin film of liquid at the aperture to
produce the finely divided liquid particles.

**![](4228a.gif)

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**US Patent # 3,864,326**

**Spraying Devices, in Particular
Nebulizing Devices**

**Robert S. Babington**

![](3864a.gif)

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**US Patent # 3,790,080** **Method of Spraying**

![](3790a.gif)



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**US Patent # 3,425,059** **Power Humidification Apparatus**

![](3425a.gif)

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**US Patent # 3,421,692** **Method of Atomizing Liquids...**

![](3421a.gif)

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